EGU2020-5835
https://doi.org/10.5194/egusphere-egu2020-5835
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

3D surface velocity variations of the Argentière glacier (French Alps) monitored with a high resolution continuous GNSS network

Andrea Walpersdorf1, Christian Vincent2, Florent Gimbert2, Agnès Helmstetter1, Luc Moreau3, Delphine Six2, Stéphane Garambois1, Laurent Ott4, Stéphane Mercier1, Olivier Laarman2, Luc Piard2, Ugo Nanni2, Marguerite Mathey1, Benoit Urruty2, Christian Sue1, Jean-Noël Bouvier1, Martin Champon5, Olivier Romeyer6, Jean-Louis Mugnier6, Mathilde Radiguet1, and the SAUSSURE GNSS team*
Andrea Walpersdorf et al.
  • 1CNRS/UGA, ISTerre, Grenoble Cedex 9, France (andrea.walpersdorf@univ-grenoble-alpes.fr)
  • 2CNRS/UGA, IGE, Grenoble Cedex 9, France
  • 3USMB, EDYTEM, Chambéry, France
  • 4CNRS/UGA/INP, GIPSA-lab, Grenoble, France
  • 5Auto-entrepreneur, La Buisse, France
  • 6CNRS/USMB, ISTerre, Chambéry, France
  • *A full list of authors appears at the end of the abstract

Five continuous GNSS stations monitor the Argentière glacier surface motion on a longitudinal profile at 2400 m altitude over a full melt season, from April to November 2019. High precision data analysis is enabled by a close-by reference station on the bedrock. This GNSS survey is part of the SAUSSURE project 2019-2022 that aims at increasing our knowledge on the physics of glacier basal sliding, by improving friction laws and validating them in a natural environment. The Argentière glacier is particularly interesting due to its long-term subglacial observatory measuring basal sliding velocity and subglacial discharge. The SAUSSURE project furthermore includes seismic, tiltmeter and piezometer measurements. The bedrock topography is obtained from a Ground Penetrating Radar.

The dense GNSS station setup permits to validate individual antenna movements. We then retrieve horizontal and vertical surface velocities on daily and sub-daily time scales. We can deduce strain rates in between the stations and their evolution in time, and relate this observable with the vertical surface motions. The confrontation of the GNSS data with independent observations allows analyzing the surface motions searching for glacier surges that combine horizontal speed-ups combined with uplift due to bed separation of the ice sheet. These events could give indications about cavity growth in spring. We will also try to investigate sub-daily motions that seem to occur in daily cycles in summer, as hinted at by the basal sliding measurements. These daily cycles are usually also seen in the seismic activity. The phase of the different features varies with respect to the daily cycles of temperature and sub-glacial water pressure. These phase offsets can give us indices on eventual mechanisms of sliding at the bedrock interface. The GNSS measurements represent a rare in situ data set that can contribute to better apprehend mechanisms of basal sliding and to provide high-resolution 3D constraints on physical models of glacier flow.

SAUSSURE GNSS team:

Andrea Walpersdorf, Christian Vincent, Florent Gimbert, Agnès Helmstetter, Delphine Six, Luc Moreau, Laurent Ott, Stéphane Mercier, Olivier Laarman, Luc Piard, Hugo Nanni, Marguerite Matthey, Benoit Urruty, Christian Sue, Jean-Noël Bouvier, Martin Champon, Olivier Romeyer, Jean-Louis Mugnier, Mathilde Radiguet, Benjamin Vial, Maxime Harter

How to cite: Walpersdorf, A., Vincent, C., Gimbert, F., Helmstetter, A., Moreau, L., Six, D., Garambois, S., Ott, L., Mercier, S., Laarman, O., Piard, L., Nanni, U., Mathey, M., Urruty, B., Sue, C., Bouvier, J.-N., Champon, M., Romeyer, O., Mugnier, J.-L., and Radiguet, M. and the SAUSSURE GNSS team: 3D surface velocity variations of the Argentière glacier (French Alps) monitored with a high resolution continuous GNSS network , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5835, https://doi.org/10.5194/egusphere-egu2020-5835, 2020